Electric contact member



Aug. 22, v1939.

H. T. BUSSMANN ELECTRIC CONTACT MEMBER Filed Dec. 16, 1936 INVENTOR.

ATTORNEY Patented Aug. 22, 1939 UNITED STATES PATENT OFFICE 7 Claims.

My invention relates to electrical contact members adapted to make disengageable contact with a cooperating contact member whereby an electric circuit may be broken under load, and is particularly applicable to contact members mounted in, on or in close association with electric insulating material commonly referred to as molded insulation, containing an organic constituent, such as Bakelite.

An object of my invention is to provide a contact member which will lessen the duration of an are which may be produced at the contact member when it is used to open a circuit when carrying current.

Another object of my invention is to provide a contact member so shaped that any are formed 'thereat will be kept as far as possible from an adjacent body of electric insulating material.

Another object of my invention is to provide a contact member adapted to be associated with a body of electric insulating material, which contact member will lessen the possibility of injury to neighboring parts by an are which might be formed at the contact member.

In the drawing:

Figure 1 is a view in section through a device comprising a contact member embodying my invention.

Figure 2 is a fragmentary view, partly in section, of a modified form of contact member embodying my invention, and

Figure 3 is a view of a contact member embodying my invention mounted on a plugfuse, which 4 is associated with a fuse holder assembly.

Referring first to Figure 1 of the drawing, I have there shown the contact member embodying my invention as operatively associated with a plug fuse holder assembly.

The assembly in this -figure'is shown as comprising a base H which includes a center contact member |3and a screw shell contact |5. A fuse holder I1 is adapted to be associated with the ,base and comprises a screw shell |9 having posi- It will be noted that the contact member 3| comprises a main body portion 33 and an end portion 35 which is of substantially frusto-conical shape, the diameters of. the end portion 35 decreasing with increase of the distances of such portions away from the body portion 3|. The end contact surface 3-] of the frusto-conical portion 35 is flat and isadapted to make abutting contact with the cooperating contact member l3.

It is here pointed out that the diameter of the 10 body portion 33 of the con-tact member 3| is only slightly less than the diameter of the opening 21 and further that as a protective electric device embodying a plug tuse body is screwed into the tubular member 3|, a center contact on the protective device will engage one end of contact member 3| and cause it to move downwardly (as seen in Figure I of the drawing) until the end contact surface 31 engages the cooperating contact member l3.

Referring now to Figure 2 of the drawing, I have there illustrated a somewhat difierent form of contact member 33, here shown as including a main body portion ll of a diameter but slightly smaller than the diameter of the opening 21, and an end contact portion 43 the diameter of which is substantially constant and appreciably less than that of the body portion 4|.

In Figure 3 I have shown a contact embodying my invention associated with a plug fuse. This 3 fuse has a body of insulating material 5| adapted to make screw threaded engagement with threads 23 of the fuse holder. A flexible disc 53 corresponds to the flexible disc 29 of Figure l and has an aperture 55 through which may be passed the 5 contact member 51 having a body portion 59 corresponding to the body portion .33, and an end portion 6| and end contact surface 63 corresponding to and respectively of Figure 1.

While as not normally int ded that the circuit including the coOperatingcontact members l3 and 3| or 51 is to be opened by unscrewing a fuse plug from the holder and thereby causing a slow separating movement of the contact member 3| or 51 from the contact member I3, it is possible that this may be done and if this happens while a current is traversing this circuit, an arc will usually result. It is obvious first of all that any are which may occur between the end contact surface .31 or 5.3 of the member 3| or 51 and the-contactmember l3 will probably start, at the contact surface 31 or 33 and will therefore be positioned a relatively large distance away from the wall 01' the opening, which wall is, as u material.

has already been stated, of electric insulating I have found in those cases where the member 25 and the member 2| are made of molded composition, that while this material is electric insulating-at ordinary temperatures, it may lose its electric insulating characteristics at higher temperatures and especially so when subjected to the influence of an electric arc. I have found also that since molded composition comprises an organic constituent there is a possibility of a vapor being given off by the material at high temperatures, which vapor under the influence of an arc may act as a conductor to increase the While I have illustrated and described certain embodiments of devices embodying my invention, I do notdesire to be limited thereto, but desire that the appended claims'shall be so construed as to cover all devices coming within the scope thereof, which scope is to be limited by the prior art only. I claim as my invention:

1. An electrical contact member adapted to be movably fitted in an opening'of a body of organic insulation material, said contact member comprising a main portion and a lesser portion being adapted to fit closely yet movably in the entrance of the opening; the smaller portion being of substantially less mass and cross-sectional area and of such restricted length that a substantial amount of the heat generated therein will be absorbed bythe main portion; the smallerportion having such reduced cross-sectional area as to leave such an enlarged space between the contact face and the walls of the opening that an are which may be formed at the contact face will not extendto said walls to injure same.

2. An electrical contact member adapted to be movably fitted in an opening of a body of insulation material, the walls of'the opening being 5 length of the arc prolong the duration e subject to carbonization by an electric arc, said It is obvious that an are formed between the contact member comprising a main portion and Cooperating Contact e s and 35 51 a lesser portion with the contact'face thereon; will be formed substantially within or'not out th ain portion having a substantial mass to Side the p p y of the end ccntactpsllrfece 3 absorb heat and being adapted to fit closely yet end h the Slope of the Sides f the p movably in the entrance of the opening; the tions 35 and ii of the contact members will tend all portion being of substantially less mass t0 keel) the 81C Within these hounds es the (115- and cross-sectional area and of such restricted tance from contact ii to any Pointcn the Sides length that a substantial amount of the heat of con t p rtions 35 and 6 a t m the generated therein will be absorbed by the main axis of the contact member will be g eater t portion; the smaller portion having such reduced the distance to y Point on the Centect m cross-sectional area as to leave such an en- Fo sim r tee- 118 t e -D 0f the Contact larged space between the contact face and the member shown iii-Figure 2 t nd to confine on walls of the opening that an are which may be C which y be formed to the end of the D formed at the contact face normally will not extion of smaller diameter 43 which portion bet to said walls t injure same.

cause of t e a er d amet r o t main body 3. The combination of an electric contact p ti H is ep way o the walls of h member and a body of insulation material hav- Cpehihg 2 during t e nti p ng moveing an opening therein; the walls of said openmeht O the cooperating contact mcmhclsing being subject to carbonization by an electric The elect insulating material surrcuhdihg arc, said contact member comprising a main ci in the contact member 3 H or 51 may portion of substantial mass to absorb heat, and a kind which. When Subjected to the adapted to fit closely yet movably in the ent influence of an arc, becomes electric conducting vtrance f said Opening and lesser portion ith r heat carbonized and after the are Strikes the contact face at the end thereof, of smaller engages this matcnahit may be Prolonged to mass, having such a restricted length that a ura increased as to its length and may substantial amount of the heat generated theretherefore-cause substantial injury to the electric m 1 be b d by the main portion, the insulating materialh Contact members h spacial relation between the lesser portion adjady mylnventlch tend to keep any arc whlch cent the contact face and the walls of the openmay e firmed between the separating whmt ing being such that an are which may be formed members away from the elect c insu mate at the contact face normally will not extend to rial and therefore greatly reduce the possibility said l to injure same. damage 0 the electric ul t material 4. An electrical contact member for a plug It wi l be o i that the m of my fuse adapted to be removably fitted in an open- Proved contact being greater at the l'emote ing of a body of organicinsulation material, said fro the arc surface will result in a tendency contact member comprising a main portion and to d are which be filmed therea-t a lesser portion with the contact face thereon, a d th s P o d an advantage i addltloh to the main portion having a substantial mass to t ose provided by the cchtmll 0 the te absorb heat and being adapted to fit closely yet. -5 memherr movably in the entrance of the opening; the

while I e mentioned "Bakelite" as smaller portion being of substantially less mass hletel'iel With Which the oontectlhember emmdy' and cross-sectional area and of such restricted e my invention-may b associated, 1 length that a substantial amount of the heat dcsh'e to be limited thereto but may use my generated therein will be absorbed by the main ")0 vention of molded mat portion; smaller ipo tion having such reduced cross-sectional area as to leave such-an enlarged space between the contact face and the walls of the opening that an are which may be formed at the contact face will notextend tosaid walls to injure same.

5. An electrical contact member for a plug fuse adapted to be removably fitted'in an opening of a body ofinsulation material, the walls of the opening being subject to carbonization by an electric are, said contact member comprisinga main portion and a lesser portion with the contact face thereon; the main portion having a substantial mass to absorb heat and being adapted to fit closely yet movably in the enwith' the contact face thereon, the main portion trance of the opening; the smaller portion being 1 having' a substantial mass to absorb heat and of substantially less mass and cross-sectional area and of such restricted length that a substantial amount of the heat generated therein will be absorbed by the main portion; the smaller portion having such reduced cross-sectional area as to leave such an enlarged space between the contact face and the walls of the opening that an are which may be formed at the contact face normally will not extend to said'walls to injure same.

6. An electrical contact member for a plug fuse holder adapted to be movably fitted in an opening of a body of organic insulation material, said contact member comprising a main lesser portion with the contact face thereon, the main portion having a subgenerated therein will be absorbed portion; the smaller portion having cross-sectional area as to leave such an enlarged space between the contact face and the walls of the opening that an are which may be formed at the contact face will not extend to said walls to injure same.

7. An electrical contact HENRY T. BUSSMANN. 

